Deformed metal composite wire

ABSTRACT

A deformed metal composite wire ( 14 ) comprises a matrix ( 12 ) of a first metal having a first melting point. The composite wire also comprises two or more filaments ( 10 ) of a second or further metal embedded ion the matrix ( 12 ) and surrounded by the matrix ( 129.  The second or further metal has a melting point which is higher or equal to the first melting point. Either the second or further metal is carbon steel or stainless steel in order to provide the necessary reinforcing or strengthening effect. The wire ( 14 ) is in a deformed state so that the two or more filaments ( 10 ) have a non-circular filament cross-section.

FIELD OF THE INVENTION

[0001] The present invention relates to a deformed metal composite wire and to a method of manufacturing such a composite wire. The present invention also relates to the uses of such a deformed metal composite wire.

BACKGROUND OF THE INVENTION

[0002] In its broadest meaning, metal composite wires are to be understood as metal wires being composed of elements being made of different metals.

[0003] Such metal composite wires are known in the art. As a matter of example patent specification GB 325 248 (filing date: 1928) discloses a composite wire to be used as an electricity conductor. This conductor wire is composed of at least three filaments. At least one filament, e.g. a steel filament, functions as a tensile member and at least one filament, e.g. a copper filament, functions as a conducting member.

[0004] Japanese patent application JP-A-09-047810 discloses a metal composite wire which is made as follows: individual steel filaments are first coated by aluminium by means of an electrolytic plating technique, the thus coated filaments are bundled and are integrally drawn so that the aluminium coating material fills up the gaps between the steel filaments. The steel filaments are not deformed.

[0005] Metal composite structures where metal filaments are separated by another metal have been described in e.g. patent specification U.S. Pat. No. 3,394,213 and in Japanese documents JP-A-51-017163, JP-A-62-260018, as a manufacturing process to make metal fibers. In all these documents, the only objective of the combination of various metals was to allow the manufacturing of very fine fibers. The function of the metal around and in between the filaments was to keep the filaments separated during the deformation. After deformation this metal is removed to obtain fibers. This metal thus is not part of the final product.

[0006] Also, the separating metal is a metal which does not melt at the temperatures of hot rolling or heat treatmentdescribed in this process (typically low carbon steel). The number of filaments is always very high, as this is the only way to obtain small sized fibers with this process (typically more than 500).

[0007] U.S. Pat. No. 3,907,550 discloses composite billets which function as starting stock for superconducting wire. Rods of a metal capable of forming a superconductor are immersed in a molten bath of ‘normal’ material, i.e. not capable of forming a superconductor. After solidification a rough billet is formed which may be subjected to high deformations which are enabled may intermediate heating treatments. The function of strengthening or reinforcing is not an issue.

[0008] According to other prior art, it is also well-known to improve flexibility of a long metal element by making a strand or rope out of finer elements (wires, filaments, . . . ). The improvement of flexibility, which is thus obtained, is countered by a reduction in strength (compared to a similar solid section long element, due to a lower filling degree), and also a lower performance of e.g. corrosion resistance and abrasion resistance. A further improvement to these cables involves the compacting of these strands or ropes (compacting, swaging, drawing): the filaments are compacted so that the filling degree increases, thus improving strength per unit of section, and to a lesser degree also improving abrasion resistance and corrosion resistance. (See e.g. patent specifications U.S. Pat. No. 3,131,469, U.S. Pat. No. 3,364,289, U.S. Pat. No. 3,130,536, U.S. Pat. No. 3,083,817. In this process the initial strand or rope can be drawn (elongated with reduction of section) only to a lesser extent (typically 30-50% elongation).

[0009] Patent application WO-A-99/23673 also describes the possibility to add in the center a filament in a softer material, which by compacting fills more easily the open spaces in between the filaments. But here again, the deformation degree is limited.

SUMMARY OF THE INVENTION

[0010] It is an object of the invention to avoid the drawbacks of the prior art. It is a further object of the invention to provide a highly deformed metal composite wire.

[0011] It is also an object of the invention to provide wires which are characterized by either a high tensile strength (i.e. substantially higher than 2000 MPa), a high corrosion resistance, a high flexibility, a high conductivity, . . . (or any combination) compared to traditional wires. It is a particular object of the present invention to provide wires with a high corrosion resistance.

[0012] According to a first aspect of the present invention, there is provided a deformed metal composite wire. This composite wire comprises a matrix of a first metal with a first melting point and two or more filaments of a second or further metal which are embedded in and surround by the matrix without leaving interstices. Either the second or the further metal or both are carbon steel or stainless steel. The second or further metals have a melting point which is higher than or equal to the first melting point. The composite wire is in a deformed state so that the two or more filaments have a non-circular cross-section.

[0013] The function of the matrix of the first metal can be multiple:

[0014] It holds the filaments together during the deformation process;

[0015] It functions as a lubricant during the deformation process;

[0016] It provides an additional property to the final deformed metal composite wire such as an anti-friction property, electrical conductivity, corrosion resistance, . . .

[0017] It provides a higher deformation and strain-hardening of the filaments. The quantity of matrix material and its volume ratio with respect to the volume of the filaments have an influence on the drawability. A volume ratio of 1 to 1 already allows a high deformation degree.

[0018] Typically the filaments in the deformed composite wire obtain a cross-section which is similar to a polygon. Due to the deformation degree, which can be very high, some “sides” of the polygon may show a very coarse aspect.

[0019] Preferably the composite wire has a round cross-section due to its drawing through a die.

[0020] The first—softer—metal may be selected from a group consisting of zinc zinc alloy, aluminium, brass, tin, tin alloy, etc . . .

[0021] The metal filaments can be present in any number, starting with a minimum number of two filaments. Typical values are between three and twenty. For most cases, the number of filaments is smaller than twenty-seven.

[0022] The metal filaments are made out of a second or further metal with a melting point higher than or equal to the melting point of the matrix material. As already mentioned, either the second metal filament or the further metal filament, or both filaments, are made of carbon steel or stainless steel in order to obtain the required strenghtening or reinforcing effect.

[0023] The metal filaments can have any size. Typical values of surface section vary between 0.01 mm² to 10 mm².

[0024] The metal filaments have the same longitudinal orientation of the wire; they can either be parallel or twisted, stranded, bunched, or cabled . . . The individual metal filaments may also have any metallic coating, of any thickness (e.g. Zn-coated steel, . . . ) and this coating can be applied by any process (electrolytic, hot dip, cladding, . . . ). Individual metal filaments without coating are possible as well.

[0025] According to the invention, a final deformation reduction of at least 50%, e.g. more than 90% or even more than 99% is possible. The terms ‘final deformation’ refer to a deformation of the composite wire without intermediate thermal treatments. The term ‘reduction’ is defined as the cross-sectional reduction and can be calculated as:

(S _(i) −S _(f))×100/S _(i)

[0026] where S_(i) is the value of the initial cross-sectional surface of the composite wire;

[0027] and where S_(f) is the value of the final cross-sectional surface of the composite wire.

[0028] The wire can hold filaments in any combination of the cases mentioned above (e.g. one carbon steel filaments surrounded by six smaller copper or aluminium filaments or one low carbon steel filament or copper filament surrounded by six high carbon steel filaments). The filaments can be positioned anywhere in the section of the wire, and can be grouped in sub-groups (e.g. 3×3 or 7×3). Some filaments can be positioned in the center of a wire cross-section (“core filaments”) and be surrounded by one or more layers of other filaments (“layer filaments”). In other embodiments, no core filaments are present and all filaments are positioned more or less at the same distance from the center point of a wire cross-section.

[0029] The metal of the filaments can have any metallurgical structure e.g. due to thermal treatments or mechanical deformation.

[0030] The metal filaments may or may not have undulations, torsions, crimp, etc . . .

[0031] According to a second aspect of the present invention, there is provided a method of manufacturing a composite wire. This method comprises the following steps:

[0032] (a) providing two or more filaments of a second or further metal;

[0033] (b) providing a matrix of a first metal with a first melting point around the two or more filaments so as to obtain a composite structure; the second or further metal have a melting point which is higher than or equal to the first melting point;

[0034] (c) deforming the composite structure to a composite wire so that the filaments have a non-circular cross-section.

[0035] The step of providing a matrix around the filaments may be done by means of an electrolytical plating step or hot dip operation, or a combination of both, whereby the electrolytical plating step precedes the hot dip operation.

[0036] The step of deforming is done by cold drawing, preferably without intermediate heat treatments.

[0037] The two or more filaments may or may not be twisted prior to providing the matrix around these two or more filaments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention will now be described into more detail with reference to the accompanying drawings wherein

[0039]FIG. 1(a), FIG. 1(b), FIG. 1(c), FIG. 1(d), FIG. 1(e) illustrate with cross-sections the subsequent steps of manufacturing a deformed metal composite wire;

[0040]FIG. 2 shows a cross-section of a deformed metal composite wire with two different types of filaments;

[0041]FIG. 3 shows a cross-section of a deformed metal composite wire where the filaments have a separate metal coating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0042] FIGS. 1(a) through 1(e) illustrate the subsequent steps of manufacturing a deformed metal composite wire according to the present invention.

[0043]FIG. 1(a) shows a cross-section of the starting material: three separate parallel filaments 10 with an initial diameter of 0.68 mm. The filaments are made of a 0.70% carbon steel. The processing of three filaments has been experienced as being easier than similar processing of four or five filaments. A higher deformation degree could be obtained for three filaments than for four or five filaments. This is probably due to the more stable construction of a 3×1 configuration in comparison with a 4×1 or 5×1 configuration and due to the smaller central “hole” of a 3×1 configuration in comparison with a 4×1 or 5×1 configuration.

[0044]FIG. 1(b) illustrates the three filaments 10 after a twisting operation, e.g. by means of a conventional double-twisting machine (buncher) or by means of a conventional tubular rotating machine. The filaments may or may not have been preformed so that a more or less open cross-section is obtained.

[0045]FIG. 1 (c) shows the cross-section after the twisted structure of three filaments 10 has left a hot dip galvanizing bath. The twisted structure is covered with a zinc matrix 12. The diameter of the galvanized 1×3 is about 1.5 mm.

[0046] The zinc coated twisted structure is then cold drawn through a series of dies. FIG. 1(d) shows an intermediate cross-section half way the series of drawing steps. The intermediate diameter of this cross-section is 0.20 mm. The intermediate tensile strength is 2850 MPa.

[0047]FIG. 1(e) shows the final cross-section of the deformed metal composite wire 14. The individual filaments 10 show within the composite wire 14 more or less polygonal cross-sections. The sides 13 of these cross-sections, which are faced with sides of other filaments, show a rough pattern due to the high deformation degree and due to an alloy layer formed between the zinc and the steel. Preferably, zinc matrix material 12 is present around each deformed filament, which means that the zinc has performed its lubricating function until the very last drawing step. The final diameter is 0.10 mm. The final tensile strength is 3840 MPa for the total cross-section. A final diameter of 0.10 mm means that a degree of reduction of 99.55% has been reached without any intermediate heat treatment.

[0048] A hot dip galvanizing bath has as result that a small iron-zinc alloy layer is created at the surface of the 3×1 steel filaments 10. This has the advantage of achieving a good adherence between the zinc matrix 12 and the steel filaments 12.

[0049] This iron-zinc alloy layer may become too brittle, e.g. if the immersion time in the zinc bath is too long. This brittleness can be avoided by decreasing the immersion times, by electroplating the 3×1 steel filaments 10 before the hot dip or by electroplating the 3×1 steel filaments to its final thickness without any hot dip step.

[0050] A deformed metal composite wire as described in relation to FIGS. 1(a) through 1(e) (3×1 steel+zinc) can be used in a lot of applications where high tensile strength, flexibility and corrosion resistance are the required properties.

[0051] An example of such an application is the use as electro discharge machining wire.

[0052] Another example of such an application is the final twisting of the wire into a 3×[3×1 steel+zinc] cord and to use it for window elevator applications.

[0053] As an alternative to the embodiment described above, brass can be used as the matrix material 12. A method to manufacture such a deformed metal composite wire with brass comprises the following steps:

[0054] 1) Patenting of steel filaments with a carbon content of 0.80% at an intermediate filament diameter of 0.68 mm;

[0055] 2) Brass coating the patented steel filaments with a thin brass coating by means of a thermodiffusion operation;

[0056] 3) Twisting three (or more) brass-coated steel filaments by means of a tubular twisting machine;

[0057] 4) Conducting the twisted 3×1 filaments through a ZnCl₂(NH₄Cl) bath;

[0058] 5) Removing the flux from the twisted structure and drying the twisted structure;

[0059] 6) Shortly (i.e. less than 1.0 second, e.g. less than 0.50 seconds) dipping the twisted structure in a hot dip brass bath, with a temperature above 930° C., and a composition according to the following lines: 62% to 70% copper (e.g. 64% Cu), 30% to 38% Zn (e.g. 36% Zn). The reason for the short dip time is that the temperature of the steel filaments must be kept so low as possible in order to avoid changes in metal structure and to limit a possible reaction of the steel with the brass;

[0060] 7) Removing the excesss amounts of brass of the brass coated structure and cooling the brass coated structure;

[0061] 8) Wet drawing the brass coated structure from a diameter of about 1.50 mm to a final diameter of 0.10 mm or even lower. During this drawing process the brass matrix functions as an excellent lubricant allowing high deformation degrees.

[0062] A deformed metal composite wire with a brass matrix can be applied as reinforcements of rubber articles such as tires, conveyor belts, timing belts.

[0063] The brass coated deformed metal composite wire can be used as such in this reinforcement or it can be bundled, or twisted together with other wires or filaments, which may be composite or not, before it is embedded in the rubber article.

[0064]FIG. 2 shows the cross-section of another deformed metal composite wire 14. This deformed metal composite wire 14 comprises a steel core filament 16 and a layer of filaments 18 made of a conducting metal such as copper or aluminium. The matrix material 12 can be zinc again or can be aluminium.

[0065] Such a metal composite wire can be used as a cable in power applications. The steel filament 16 functions as the tensile member while the copper or aluminium filaments function as the electrical conducting elements. The matrix material 12 provides an additional corrosion protection. Such a metal composite wire can have a high tensile strength due to the steel core filament and the high degree of deformation and a high flexibility due to its composite nature.

[0066] Other embodiments are also possible for this 1+6 configuration. A core filament 16 softer than the six layer filaments 18 can be chosen. If the six layer filaments are of a high carbon steel (carbon content above 0.6%), the core filament may of a low carbon steel (% C lower than 0.5%), of copper, or of aluminium.

[0067] In the case of a 1+6 configuration, it has shown that it is advantageous to have as starting configuration a core filament with a diameter somewhat greater than the diameter of the six layer filaments. This improves penetration of the metal matrix material into the strand and improves drawability.

[0068]FIG. 3 shows yet another cross-section of a deformed metal composite wire 14. The difference with the metal composite wire of FIG. 1(e) is that the steel filaments 10 are now coated with a metallic coating 20.

EXAMPLES AND RESULTS

[0069] 1. Stainless Steel in 3×1 Configuration

[0070] Stainless steel wires with composition 316L are drawn from 1.50 mm to a 0.50 mm filament. Three filaments are twisted into a 3×0.50 mm (external diameter of composite wire equal to 1.08 mm), hot dipped in zinc and subsequently drawn. The composite wire has been drawn without any problem to an external diameter of 0.15 mm, i.e. far beyond the normal drawability of stainless steel wire. The initial metal section of the stainless wire (diameter 1.50 mm) has been reduced to a metal section with a diameter of approximately 0.07 mm within the cross-section of the deformed composite wire. This is equivalent to an effective reduction of 99.8% without intermediate heat treatment.

[0071] 2. Carbon Steel in 3×1 Configuration—Tensile Strength

[0072] The tensile strength R_(m) of a single filament (reference) has been compared with the tensile strength of a deformed composite wire (invention). Both the single filament and the filaments of the composite wire are of a 0.70% C carbon steel. The three filaments in the composite wire have been galvanized. In case of the invention there is clearly a considerable gain in tensile strength due to the increased deformation. Table 1 summarizes the results. TABLE 1 Final Total diameter reduction Tensile strength Starting product

(mm) (%) R_(m) (MPa) 0.68 mm reference 0.12 96.9 2914 3 × 0.68 mm invention 0.12 99.3 3747 0.76 mm reference 0.15 96.1 2792 3 × 0.68 mm invention 0.15 99.0 3422 3 × 0.76 mm invention 0.15 99.2 3569

[0073] 3. Carbon Steel in 3×1 Configuration—Corrosion Resistance

[0074] The corrosion resistance of a single galvanized wire has been compared with the corrosion resistance of a deformed composite wire according to the invention.

[0075] Table 2 mentions the time span it takes until the first spots of dark brown rust (DBR) and until 5% of the surface is covered with dark brown rust. TABLE 2 1^(st) DBR spots (hrs) % DBR (hrs) 0.15 mm reference wire  2  3 (comprises 3 filaments) 0.15 mm invention wire 20 24

[0076] 4. Properties of Ropes or Cords Made Out of Deformed Composite Wires.

[0077] A 0.15 mm deformed composite wire (comprised three filaments) according to the invention has been used to make a 3×3×0.15 mm cord. This cord has been compared with a lightly galvanized 3×3×0.15 mm cord and with a heavily galvanized 3×3×0.15 mm cord. Table 3 mentions the results. TABLE 3 3 × 3 × 0.15 3 × 3 × 0.15 lightly heavily 3 × 3 × 0.15 galvanized galvanized invention wire Tensile strength 2669 2705 3083 R_(m) (MPa) Total elongation 2.12 2.05 2.33 at fracture (%) Total zinc 19.69 80.1 157.12 weight (g/kg) 1^(st) DBR spots 4 16 26 (hrs) 5% DBR 5 17 33 Hunter dry 1080 780 980 fatigue (MPa) Hunter wet 750 640 720 fatigue (MPa) Number of 50932 10779 23314 bending cycles before fracture 

1. A deformed metal composite wire comprising a matrix of a first metal having a first melting point, two or more filaments of a second or further metal embedded in said matrix and surrounded by said matrix, said second or further metal having a melting point which is higher or equal to the first melting point, either said second or further metal or both are carbon steel or stainless steel, said wire being in a deformed state so that said two or more filaments have a non-circular filament cross-section.
 2. A composite wire according to claim 1 wherein said wire has a round wire cross-section.
 3. A composite wire according to any one of the preceding claims wherein said first metal is selected from a group consisting of zinc, zinc alloy, aluminium, brass, tin, tin alloy.
 4. A composite wire according to any one of the preceding claims wherein an alloy layer is formed between said first metal, on the one hand, and said second or further metal, on the other hand.
 5. A composite wire according to any one of the preceding claims wherein said wire has been subjected to a final deformation reduction of at least 50%.
 6. A composite wire according to any one of the preceding claims wherein said wire comprises up to twenty-seven filaments.
 7. A composite wire according to any one of the preceding claims wherein said filaments show a twisting step around each other, said twisting step being greater than 50 mm.
 8. A composite wire according to any one of claims 1 to 6 wherein said filaments are parallel to each other.
 9. A composite wire according to any one of the preceding claims wherein said second metal differs from said further metal.
 10. A composite wire according to any one of the preceding claims wherein said wire has a cross-section showing a core of one of more filaments and one or more layers of filaments around the core.
 11. A composite wire according to any one of claims 1 to 9 wherein said wire has a cross-section without central core filaments.
 12. A composite wire according to any one of the preceding claims wherein said composite wire has a tensile strength greater than 2000 MPa.
 13. A composite wire according to any one of the preceding claims wherein first metal is present surrounding every filament.
 14. A composite wire according to any one of the preceding claims wherein one or all of the filaments are individually provided with a coating of a metal.
 15. A composite wire according to any one of the preceding claims where said filaments are waved or undulated.
 16. Use of a composite wire according to any one of the preceding claims as an electro-discharge machining wire.
 17. A method of manufacturing a composite wire, said method comprising the following steps: (a) providing two or more filaments of a second or further metal; (b) providing a matrix of a first metal around said two or more filaments so as to obtain a composite structure where the filaments are embedded in the matrix and surrounded by the matrix, said first metal having a first melting point, said second or further metal having a melting point which is higher or equal to the first melting point; (c) deforming said composite structure to a composite wire so that the filaments have a non-circular cross-section.
 18. A method according to claim 17 wherein the step of providing a matrix around said filaments is done by means of a hot dip operation.
 19. A method according to claim 17 or 18 wherein the step of deforming is done by cold drawing.
 20. A method according to claim 19 wherein said cold drawing is done without intermediate heating steps.
 21. A method according to any one of claims 17 to 20 wherein said two or more filaments are twisted prior to providing said matrix around said two or more filaments.
 22. A metal rope comprising one or more composite wires according to any one of claims 1 to
 15. 